1. Field of the Invention
The present invention is related to a motor for use in office automation devices such as the magnetic hard disc drive device (HDD), video tape recorder (VTR) and laser beam printer (LBP).
2. Related Art of the Invention
The motor for the office automation devices generally comprises a rotor with a magnet fixed to it and a stator with a coil fixed to it. The rotor or stator is provided with a housing, and a rolling bearing is provided between the housing and a shaft.
Conventionally, an adhesive is used to fix the rolling bearing between the shaft and the housing in the office automation devices. For example, in order that the inner race is fixed to the shaft, a groove is formed around the shaft, and the adhesive is provided between the groove and the inner peripheral surface of the inner race, so that the uniform bonding is made in the circumferential direction.
According to the publication of JP Patent No. 2890159, the outer peripheral surface of the shaft is formed with a knurled portion and a circumferential groove, and an adhesive is put in between the grooves of the knurled portion and the inner peripheral surface of the inner race and into the circumferential groove to fix the inner race to the shaft. In addition, there is a case that the rolling bearing is fixed to the inner race through press-fitting with no adhesive used.
The inner peripheral circle of the inner race and the outer peripheral circle of the shaft in cross section could not be complete in roundness, and therefore the thickness of the adhesive is inclined to be uneven in the circumferential direction even if the knurled portion and the circumferential groove are formed. As a result, the expansion and shrinkage forces of the adhesive may be so uneven in the circumferential direction that the races are deformed and that the rotation precision of the motor is worsened. For example, the non-repetitive runout (NRRO), that does not synchronize with the rotation, may be caused in the motor.
On the other hand, upon press-fitting, the precision (roughness) of the surfaces press-fitted is transferred to the raceway to deform the race.
Taking such problems into consideration, an objective of the present invention is to provide a motor comprising a rotor and stator where a rolling bearing is provided between a housing provided in a rotor or stator and a shaft, such that the races of the rolling bearing is prevented from being deformed and that the rotation precision of the motor is improved.